This is needed so that SVG files are included as an <object...> rather
than as an <img...>, which in turn is needed to ensure SVG tooltips
will work. We do not explicitly require org-mode 9.1, but we install
it if it is not present.
* HACKING: Mention the requirement.
* doc/org/.dir-locals.el.in, doc/org/init.el.in, doc/org/spot.css:
Adjust to org-mode 9.1.
* doc/Makefile.am: Run emacs with the site-lisp libraries, in
case it contains a more recent org-mode.
* elisp/ob-dot.el: Delete, this was a work around older versions.
* elisp/Makefile.am: Adjust.
* doc/org/tut51.org: New file.
* doc/org/tut.org, doc/Makefile.am, NEWS: Add it.
* elisp/ob-dot.el: New file, to work around old org-mode versions.
* elisp/README, elisp/Makefile.am: Add it.
* elisp/hoa-mode.el, elisp/Makefile.am, elisp/README: New files.
* debian/copyright, configure.ac, README, Makefile.am: Adjust.
* doc/org/init.el.in: Adjust to load hoa-mode.el.
* doc/org/spot.css: Add entries for HOA mode.
* doc/org/hoa.org, doc/org/ltldo.org, doc/org/oaut.org,
doc/org/tut20.org, doc/org/tut21.org, doc/org/tut22.org,
doc/org/tut30.org: Make the HOA outputs as HOA.
